The present invention relates to a metal mold for tire vulcanization.
Hitherto, the following three kinds of metal mold are employed for molding a tire.
(1) A metal mold comprizing an upper and a lower tread rings 50 having an uneven molding portion (P') corresponding to a tread pattern P as shown in FIGS. 6 and 7. The tread rings 50 are made by casting Aluminum and set in a shell 51 made of a cast steel or a cut steel block.
(2) A metal mold comprizing small pieces (pattern segments) 52 having a molding portion corresponding to a tread pattern P as shown in FIG. 8. The small pieces 52 are made by casting Aluminum and arranged in order in a circumferential direction and set in the similar shell as described above.
(3) A metal mold comprizing a mold made of, for example, a cast steel on which a tread pattern P is engraved directly.
The above-mentioned conventional metal molds, however, need expensive working machines, and require long working time and high manufacturing cost because of greater part of manual working since it is difficult to produce working data and to mechanize the working.
These types of metal molds also require a large number of vent holes for venting air when the vulcanization of a tire is carried on. Furthermore, in case of mending flaws caused by the fall of articles on the molding surface and blowholes of Aluminum casting, and in case of changing a tread pattern partly, and the like, these types of metal molds require long working time and high cost because of the necessity of manual operation and Aluminum welding.
The object of the present invention is to provide a metal mold for tire vulcanization which is easy to work and conveninent for mending, changing, and the like.